Tiny Ozarks frog heralds end of winter with its mating call

The spring peeper’s high-pitched call can be heard on warm spring nights and during the day in early summer and autumn. This species spends most of its time on the forest floor or in low shrubbery. The frogs live near ponds, streams and swamps where there is thick undergrowth.
(Photo:
Missouri Department of Conservation
)

Bird sounds are among the best-known harbingers of spring in the wildlife world, but in this area, a frog begins spreading the message of seasonal change at a time many birds are still warming up their singing voices.

The spring peeper is one of the Ozarks' well-known end-of-winter signs because it is the earliest-calling frog of the spring. Although it may sound odd to talk about spring in the same week that featured snow, ice and school closings, this is the time to talk about spring peepers. These small frogs begin calling and breeding in early March (some years in late February) and continue until early May.

Enjoying spring peepers is a listening experience, not a visual one. The frog grows only to slightly more than an inch in length; most could fit comfortably on the end of your finger. The most noticeable characteristic of this frog is the clear, high-pitched call the male uses to attract females.

The spring peeper makes this call by closing its mouth and nostrils and forcing air from the lungs over its vocal cords into the lower part of the mouth, which inflates into a bubble and vibrates like a drum. This process produces loud trills. A spring peeper's vocal sac can inflate to about the size of a quarter.

As is the case with all wildlife mating calls in the spring, the more clear and robust the call, the better chances of attracting a female. These calls are heard primarily at dusk and at night, although they can be heard on overcast days during a rain or immediately after one.

Spring peepers survive winter by digging into the soil. As with a number of frogs and toads, spring peepers produce a type of "antifreeze" in their blood that protects their tissues from damage if they become frozen.

The general color of a spring peeper varies from pinkish to light tan, brown or gray. Spring peepers also feature a dark "X" marking on their backs. However, as previously stated, describing how they look is basically irrelevant because you'll hear them far more often than you'll see them. It should be noted that the type of spring peeper that lives in Missouri is the northern spring peeper, which is found throughout much of the eastern United States.

The southern spring peeper is only found in the extreme southeastern portion of the country.

The northern spring peeper is primarily a woodland species. It lives near ponds, streams or swamps where there is thick undergrowth.

The result of all this calling and courtship is egg-laying. One female can lay up to 900 eggs, each egg about 1 millimeter in size. The eggs are laid singly and are attached to leaves, grasses and sticks in shallow water. They are fertilized by males as they are laid. The eggs hatch in three or four days, and tadpoles metamorphose in about two months.

More information about spring peepers and other amphibians is at your nearest Missouri Department of Conservation office or at www.missouriconservation.org.

Francis Skalicky is media specialist for the Missouri Department of Conservation's Southwest Region. For information about conservation issues, call 417-895-6880.